1. Field
Various features pertain to local oscillator signal generation, and more particularly, to a system, apparatus, and method for low power local oscillator signal generation for single band and multi-band transceivers.
2. Background
FIG. 1 illustrates a functional block diagram of an integrated circuit (IC) multi-band receiver 100 found in the prior art. In this example, the multi-band receiver 100 is a tri-band receiver (e.g., receives signals in the 850 MHz, 1900 MHz, and 2100 MHz bands) for a mobile device. Band A 110 includes a low noise amplifier (LNA) 112, a high power, high gain mixer 114, and local oscillator signal path circuitry 116. Similarly, Band B 120 and Band C 130 also include LNAs 122, 132, high power, high gain mixers 124, 134, and local oscillator signal path circuitry 126, 136. Bands A 110, B 120, and C 130 may receive radio frequency (RF) input signals SIz at one or more input terminals of the LNAs 112, 122, 132.
The LNAs 112, 122, 132 amplify (if needed) the RF signals received, and the mixers 114, 124, 134 down-convert the RF signals to baseband (BB) or intermediate frequencies. The receiver 100 also includes a voltage controlled oscillator (VCO) 102 that provides a local oscillating (LO) signal to the mixers 114, 124, 134 for performing down-conversion. FIG. 2 illustrates a functional block diagram of an LO signal path circuitry 200 found in the prior art that may include one or more active buffers 202, 206 and/or a frequency divider 204. The LO signal path circuitry 200 may be representative of the circuitry 116, 126, 136 that supplies the LO signal from the VCO 102 to the mixers 114, 124, 134.
Referring to FIG. 1, the physical location (i.e., placement on chip and routing) of the LNAs 112, 122, 132 are frequently required to be as close as possible to the RF input signal pins (responsible for receiving the RF input signals SIZ) of the integrated circuit receiver 100 in order to minimize wire length, and consequently minimize the noise injected onto the received RF signals. For example, the LNAs 112, 122, 132 may be placed (e.g., routed) on the IC receiver 100 close to their respective RF input signal pins. Similarly, the mixers 114, 124, 134 may be placed close to their corresponding LNAs 112, 122, 132. However, due to size and/or cost constraints the receiver 100 may have only one VCO 102. As a result, the VCO 102 may be placed on the IC receiver 100 further away from some bands' mixers than other bands' mixers.
In the illustrated example, the VCO 102 is placed close to Band A's mixer 114, but further away from Band B and Band C's mixers 124, 134. The longer circuit path from the VCO 102 to Band B 120 and Band C 130 means that Band B's LO signal path circuitry 126 and Band C's LO signal path circuitry 136 may need to consume more power to propagate the LO signal from the VCO 102 to Band B 120 and Band C's 130 respective mixers 124, 134. For example, Band B and Band C's LO Path circuitry 126, 136 may need buffers 202, 206 and/or frequency divider(s) 204 that are scaled to be larger than the buffers and/or frequency divider(s) of Band A's LO Path circuitry 116 in order to properly supply the LO signal from the VCO 102 to the mixers 124, 134. Larger and/or additional buffers and frequency dividers results in increased current and power consumption.
In effect, prior art transceivers undesirably consume significant power in order to propagate LO signals from a VCO to certain on-chip mixers that are placed further away from the VCO than other mixers. Therefore, there is a need for reducing power consumption associated with providing mixers an LO signal where the mixers are placed relatively far from an IC transceiver's VCO.